Gender differences in rotation of the shank during single-legged drop landing and its relation to rotational muscle strength of the knee.
BACKGROUND
Increased shank rotation during landing has been considered to be one of the factors for noncontact anterior cruciate ligament injuries in female athletes. There have been no known gender differences in rotational knee muscle strength, which is expected to inhibit exaggerated shank rotation.


OBJECTIVE
Women have less knee external rotator strength than do men. Lower external rotator strength is associated with increased internal shank rotation at the time of landing.


METHODS
Controlled laboratory study.


METHODS
One hundred sixty-nine healthy young subjects (81 female and 88 male; age, 17.0 +/- 1.0 years) volunteered to participate in this study. The subjects performed single-legged drop landings from a 20-cm height. Femoral and shank kinematics were measured using a 3D optoelectronic tracking system during the drop landings, and then the joint angles around the knee (flexion/extension, valgus/varus, and internal/external rotation) were calculated. The maximal isometric rotational muscle strength of the knee was measured at 30 degrees of knee flexion in a supine position using a dynamometer.


RESULTS
The female subjects had significantly less external shank rotation strength than did the male subjects (P < .001). Female subjects also exhibited significantly greater peak shank internal rotation angles than did males during landing (P < .05). Moderate but significant association was found between the maximum shank external rotation strength and the peak shank internal rotation angle during landing (r = -0.322, P < .01).


CONCLUSIONS
Female subjects tended to have poor shank external rotator strength. This may lead to large shank internal rotation movement during the single-legged drop landing.


CONCLUSIONS
Improving strength training of the external rotator muscle may help decrease the rates of anterior cruciate ligament injury in female athletes.
Kiriyama
Shinya
S
Clinical Kinesiology Laboratory, Kitasato University Graduate School of Medical Science, Kanagawa, Japan.
Sato
Haruhiko
H
Takahira
Naonobu
N
D000293:Adolescent; D000070598:Anterior Cruciate Ligament Injuries; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D007718:Knee Injuries / Q000209:etiology; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D053580:Muscle Strength; D012399:Rotation; D012737:Sex Factors; D016474:Weight-Bearing